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Reverse Method (Int32, Int32)
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List(Of T).Reverse Method (Int32, Int32)

Reverses the order of the elements in the specified range.

Namespace:  System.Collections.Generic
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
Public Sub Reverse ( _
	index As Integer, _
	count As Integer _
)

Parameters

index
Type: System.Int32
The zero-based starting index of the range to reverse.
count
Type: System.Int32
The number of elements in the range to reverse.

ExceptionCondition
ArgumentOutOfRangeException

index is less than 0.

-or-

count is less than 0.

ArgumentException

index and count do not denote a valid range of elements in the List(Of T).

This method uses Array.Reverse to reverse the order of the elements, such that the element at List(Of T)[i], where i is any index within the range, moves to List(Of T)[j], where j equals index plus index plus count minus i minus 1.

This method is an O(n) operation, where n is Count.

The following code example demonstrates both overloads of the Reverse method. The code example creates a List(Of T) of strings and adds six strings. The Reverse method overload is used to reverse the list, and then the Reverse(Int32, Int32) method overload is used to reverse the middle of the list, beginning with element 1 and encompassing four elements.


Imports System
Imports System.Collections.Generic

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs As New List(Of String)

        dinosaurs.Add("Pachycephalosaurus")
        dinosaurs.Add("Parasauralophus")
        dinosaurs.Add("Mamenchisaurus")
        dinosaurs.Add("Amargasaurus")
        dinosaurs.Add("Coelophysis")
        dinosaurs.Add("Oviraptor")

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        dinosaurs.Reverse()

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        dinosaurs.Reverse(1, 4)

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

    End Sub
End Class

' This code example produces the following output:
'
'Pachycephalosaurus
'Parasauralophus
'Mamenchisaurus
'Amargasaurus
'Coelophysis
'Oviraptor
'
'Oviraptor
'Coelophysis
'Amargasaurus
'Mamenchisaurus
'Parasauralophus
'Pachycephalosaurus
'
'Oviraptor
'Parasauralophus
'Mamenchisaurus
'Amargasaurus
'Coelophysis
'Pachycephalosaurus


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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